Description of the Hardware
EPC9 Manual
13
Clipping
: This LED lights whenever an amplifier saturates in the current monitor
pathway. The indicator is important in voltage-clamp experiments where capacitive
artifacts will be subtracted in a computer; the subtraction will work well only as long
as no saturation occurs, and this indicator serves as a simple monitor of this
condition. It is particularly useful since it will indicate clipping by internal amplifiers
even in cases where, because of filtering, the output voltage is not saturated.
Digital Bus
: This LED lights whenever digital information is sent from the computer
to the EPC9 amplifier.
AD Inputs
: The built-in laboratory interface (ITC-16) provides eight AD channels (0-
7). AD channels 6 and 7 are internally connected to the EPC9 and are used by the
software supplied. Channel 6 is labeled “I-Mon” and carries the
Current Monitor 2
output. Channel 7 carries the output of the EPC9's internal multiplexer, which in
most operating modes is set to the voltage monitor signal. You normally should not
connect anything to channel 6 and 7, unless you wish to inspect the signals for
diagnostic reasons. However, channels 0-5 are freely available for application
programs. For example, the
Pulse
program can use these channels to monitor
temperature, pressure or outputs from other sensors.
DA Outputs
: Four DA channels are provided (0-3). They carry the following signals:
• DA-0 - Free (
C-slow
during
Cap. Track
)
• DA-1 - Free (
G-series
during
Cap. Track
)
• DA-2 - Test output (used in self-test and calibration)
• DA-3 - Internal stimulus output (used to monitor the stimulus)
Note:
These are output connectors! Make sure that you never feed stimuli into these
outputs.
DA-1 is typically used to trigger an oscilloscope or an isolation unit. In the
Capacitance-Tracking
mode of
E9Screen
, DA channels 0 and 1 can be used to provide
optional special-purpose outputs. DA-2 can be used to inject test signals into the
EPC9 circuitry in the
Test
mode (see
Chapter
Measuring the Frequency Response
on
page 34
). DA-3 is wired internally as the internal stimulus generator.
The specific DA-channel assignments are made in the software (see
Pulse Manual,
Chapter 6 - EPC9 Amplifier
). DA channel 2 (
Test
) should normally not be used. Also,
DA-3 should normally not be used to monitor the stimulus output, because this may
degrade the noise performance of the EPC9. The buffered
Voltage Monitor
output
should be used instead. The voltage at the connector is 10 times the nominal
stimulus amplitude.
